Electrostatically shielding contacts for high potential switch



Jan- 4, 1966 J. c. w. RANsoM 3,227,830

ELECTROSTATICALLY SHIELDING CONTACTS FOR HIGH POTENTIAL SWITCH Filed Nov. 26, 1963 United States Patent O 3,227,830 ELECTROSTATICALLY SHIELDING CONTACTS FOR HIGH POTENTIAL SWITCH .lames C. W. Ransom, Portland, Oreg., assignor, by mesne assignments, to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Nov. 26, 1963, Ser. No. 326,018 6 Claims. (Cl. 200-48) This invention relates to a high potential switch, more specifically to a high potential switch with an improved contact assembly.

The switch of this invention is intended to operate at a high potential, for example 750 kv. In the electrostatic field in the neighborhood of a switch at high potential, the gradients may be high enough to ionize the air and produce corona. Switch manufacturers usually provide electrostatic shields to prevent corona. A shield has conductors that establish a region of equipotential; these conductors are shaped to establish a gently sloping equipotential surface and an associated region of low gradient. A common shape for a shield is a ring; sometimes several rings are arrayed to establish an equipotential surface that is a generally cylindrical shape with rounded ends.

One object of this invention is to provide a new and improved high potential switch that uses a ringlike contact structure that is somewhat like the electrostatic shielding rings used with high potential switches that have separate contact engaging elements.

The switch of this invention has two relatively movable contact elements that are each shaped to provide a low gradient electric lield and to interlock with each other. In the specific switch that will be described, each contact element comprises a pair of conductive rings and associated structure to hold the rings parallel and spaced apart. The two pairs of rings are oriented on the switch operating structure so that in the closed position the rings interlock and make electrical contact.

One of the advantages of this structure is that the contact structure is held in engagement by the spring of the contacts and without particular force from the insulator stacks. Another advantage of this switch is that the structure provides several points of electrical contact between the two sets of contacts. Electrical contact takes place at predetermined points where the contact structure can be provided with suitable contact making material. Another advantage of the switch is that the two contact structures can be identical and that rings are readily available and their electrical shielding characteristics are known.

The drawing and the detailed description of the invention will suggest other objects and advantages of the switch.

In the drawing:

FIG. 1 is a front view of the high potential switch of this invention; and

FIG. 2 is an isometric view of the Contact making elements of the switch of FIG. 1.

Introduction-As FIG. 1 shows, the switch and the associated structure is made up of two substantially identical groups of components. Similar components are given the same identifying number and are distinguished by letter suffixes a and b; similar components will be referred to collectively by number without the suix. The switch of this invention has two units 10a and 10b that operate to control the circuit between two conductors 11a and 11b. Because conductors 11a, 11b are at a high potential, the two switch units 10a, 10b are mounted on stacks of insulators 12a and 12b. These insulators are supported by suitable structures 13a and 13b that may be at ground potential. Each switch unit 10a, 10b includes 3,227,830L Patented Jan. 4, 1966 ICC a pole 18, a supporting and actuating mechanism 19 for carrying pole 18, and a contact assembly 20 mounted on the unsupported end of pole 18.

The supporting and actuating mechanism. The supporting and actuating mechanism 19 comprises a frame 22, a pin 23 that pivotably supports pole 18, a Huid motor 24 having a movablepiston rod 25, a linkage 26 connecting the ram of the fluid motor to swing pole 18 about pin 23, and a brush and terminal assembly 30 that electrically connects pole 18 to the associated line conductor 11. Hydraulic motor 24 is connected to be energized through a hydraulic line'31 that extends through the insulator stack 12 to a supply of pressurized fluid. Fluid motor 24 operates the associated pole 18 to swing in a vertical arc to open and close the switch.

The' Contact assembly-Each contact assembly 20 comprises a pair of rings 35, 36 and a support 37 that mechanically and conductively connects the rings to the associated pole 18. Preferably each support is located within the region shielded by the associated pair of rings 35, 36. Preferably rings 35, 36 are identical and are spaced apart by slightly less than their outside diameter. As FIG. 2 shows, pairs of rings 35a, 36a, and 35b, 36h are rotated apart on the associated pole 18 so that when the switch is closed the rings intert with pair 35a, 36a perpendicular to the plane of movement of pole 18a, and with pair 35h, 36b parallel to the plane of movement of pole 1811. The structure is made suiciently flexible for the rings to move into engagement and to provide a spring force holding the contacts together when the switch is closed. The rings Contact each other at four points and inserts 38 of suitable contact making material may be located at these points.

The rings 35, 36 are shaped to help prevent corona. Because the material is conductive, the rings and the pole of one switch section are at a uniform potential (except for voltage drops associated with line current conduction). The air space inside the pairs of rings is at substantially the same potential as the conductive portion of the rings and thus a single contact assembly 20 has the electrical effect of a rather large somewhat cylindrically shaped continuous conductive surface with smoothly rounded edges. When pairs of rings 35a, 36a and 35h, 36b are interlocked they establish a rather spherical shaped equipotential surface. Thus, in the region of the rings the equipotential surfaces are gently sloping and the voltage gradients are correspondingly low.

The rings 35, 36 that are shown in the drawing are simple to construct, provide four points of contact, and easily fit together to open and close. The two poles can be opened and closed in synchronism or slightly out of synchronism and the contact assemblies 20a, 20h open and close properly.

Other embodimentsr-The rings 35, 36 will open and close satisfactorily when mounted at various angles on poles 18a, 18b. The rings can be modified in size and shape to provide more points of electrical contact or to establish a low gradient region with different equipotential surfaces.

One of the advantages of the switch of FIG. l is that the contacts move in a vertical plane and three sets of switches for a three phase system can be mounted rather close together; the ring arrangement of this invention can also be used with switches of the type in which the pole is swung in horizontal arcs or in any other plane.

Those skilled in the art will recognize other modifications and variations within the spirit of the invention and the scope of the claims.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

1. A switch comprising,

a rst and a second contact assembly each comprising a pair of rings and means spacing said pair apart a predetermined distance, said rings being shaped to prevent corona at a predetermined potential, and

an Operating mechanism for producing relative motion between said contact assemblies to open and close said switch,

said pairs of rings being oriented on said operating mechanism to intert in electrical contact when said switch is closed.

2. A switch according to claim 1 in which said rings of each pair are spaced apart coaxially parallel and are oriented on said mechanism to intertt with the planes of the rings of said first pair perpendicular to the planes of the rings of said second pair.

3. A switch according to claim 2 in which said contact assemblies are mounted on poles that are swingable on coplanar arcs, and said rings of said first pair are perpendicular to the plane of said arcs, and said rings of said second pair are parallel to said plane.

4. A switch according to claim 3 in which said mechanism operates to swing said Contact assemblies in synchronism.

5. A switch according to claim 3 in which said spacing means is resilient to provide a force holding said contact assemlies in engagement when said switch is closed and permitting said assemblies to spring in and out of engagement when said mechanism is operated.

6. A switch according to claim 5 in which each said spacing means is located within the space electrically shielded by the associated pair of rings.

References Cited by the Examiner FOREIGN PATENTS 204,611 8/ 1939 Switzerland.

KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. A SWITCH COMPRISING, A FIRST AND A SECOND CONTACT ASSEMBLY EACH COMPRISING A PAIR OF RINGS AND MEANS SPACING SAID PAIR APART A PREDETERMINED DISTANCE, SAID RINGS BEING SHAPED TO PREVENT CORONA AT A PREDETERMINED POTENTIAL, AND AN OPERATING MECHANISM FOR PRODUCING RELATIVE MOTION BETWEEN SAID CONTACT ASSEMBLIES TO OPEN AND CLOSE SAID SWITCH, SAID PAIRS OF RINGS BEING ORIENTED ON SAID OPERATING MECHANISM TO INTERFIT IN ELECTRICAL CONTACT WHEN SAID SWITCH IS CLOSED. 